Understanding the many processes that influence ground level concentrations of greenhouse gases and air quality pollutants is crucial to interpreting the impact of anthropogenic atmospheric emissions. In particular, characterising the role of the road transport sector as a major emission source enables improved assessment of the available abatement opportunities. The present study utilises both atmospheric modelling and monitoring to evaluate the current variation in carbon dioxide and nitrogen oxides across London and the wider UK. The potential benefits of future road transport scenarios are assessed through an Integrated Assessment Model. The analysis should be of interest to professionals concerned with the climate change and air quality benefits of adopting hybrid buses and fully electric vehicles in urban areas.